GSHPhysics11 - Chapter 3

3.1 - Horizontal Motion and Friction

> Kinematics: Mathematical description of motion (developed by Galilleo)
> Dynamics: Why the objects move the way they do.
> Limiting Static Friction: When surfaces are NOT sliding past.
Resistance to the start of motion.
> Kinetic Friction: The forces that opposes the motion of an object once it is moving.
> Normal Force: A supporting force acting perpendicular to the surface.

>Friction: The force opposing motion whenever one surface moves or tends to move with reference to another.

> Types of Friction:

1. Sliding friction: Surfaces sliding past one another. 2. Rolling friction: Opposes the motion of one surface rolling over another. (For example, a tire rolling on the ground) 3. Fluid friction: Moving through a gas or liquid. (For example, air resistance and/or drag)

Places where friction is desired: Between us and outside world.
Places where friction is NOT desired: Moving a large object (For example, a refrigerator)

Normal Force - A supporting force acting perpendicular to the surface. (Doesn’t have to be vertical)
(Remember: Force of gravity always goes towards the center of the Earth.)

Ff varies FN - If there is large normal force the friction force is large as well and the opposite is true. For example, if we were trying to move Mr. Cote and a student in our class we would need more force to move him than we would need to move the student. However, if Mr. Cote was on roller blades and the student wasn’t, it’d be easier to move him so there would need to be more force on the student to move them.

......... Greek letter Mu (uppercase Μ, lowercase μ)

> Mk:Coefficient of kinetic friction.
>Ms:Coefficient of static friction.
Ff=Mk*Fn & |Ff|=Mk|Fn|

(Where 'Ff' is the size of friction acting as the surfaces slip past each other.)

Ff=Ms*Fn

(Where Ff is the size of friction acting to get the surfaces to START to slip past each other)

Newtons First Law of Motion
(Law of Inertia)

Developed from Galileo's thought experiment of inertia.

Every object will continue in a state of rest or constant speed in a straight line unless acted upon by an external unbalanced or net force.

Example: When you are shoveling snow you pick the snow up and throw it. After you throw the snow you stop applying force to it. The snow however keeps traveling until it touches the ground.

Newton's Second Law of Motion

If there is a net force on a object, the object accelerates.
The acceleration is directly proportional to the net force and the the acceleration is inversely proportional to the objects mass.
the acceleration is in the same direction as the net force.
" directly proportional" means that if the net force is doubled the acceleration doubles.
"inversely proportional" means that if the mass doubles, the acceleration will be half as much

so basically,
When a net force acts on an object, the object accelerates in the direction of the net force. Acceleration is directly proportional to the net force and inversly proportional to the mass of the object.
Force: how much an object will accelerate
Pressure: determines how that acceleration will feel.It depends on force( it is directly proportional to force), area over which the force is applied.( it is inversely proportional to area)

NEWTON’S THIRD LAW OF MOTION
Whenever one object exerts a force on a second object, the second object exerts a force that I equal in magnitude and opposite in direction on the first object.
( for the diagram please look at the folder below:)

NEWTON.docx